1. MUTATIONS

2. What are Mutations? Mutations are changes in the genetic material.
Kinds of Mutations:
Mutations that produce changes in the number or structure of chromosomes are known as chromosomal mutations.
Mutations that produce changes in a single gene are known as gene mutations.

3. Chromosomal Mutations
Recall that chromosomal abnormalities often result from nondisjunction, the failure of chromosomes to separate properly during meiosis. Nondisjunction results in sex cells that have too many or too few chromosomes. If these abnormal sex cells are used for fertilization, the offspring will have an abnormal chromosome number.
Monosomy – missing a chromosome
Example: Monosomy X or Turner Syndrome
Trisomy – having an extra chromosome
Example: Trisomy 21 or Down Syndrome

4. Turner Syndrome

5. Down Syndrome

6. Chromosomal Mutations
Recall the 4 types of chromosomal mutations that involve changes in chromosome structure due to breakage:
Deletion
Duplication
Inversion
Translocation

7. Gene Mutations
A gene mutation is a change in the nucleotide sequence of a gene.
Gene mutations involving a change in one or a few DNA nucleotides are known as point mutations because they occur at a single point in the DNA sequence.
Point mutations include substitutions, insertions, and deletions.

8. Normal Gene Normal gene GGTCTCCTCACGCCA ↓ DNA CCAGAGGAGUGCGGU Codons
Pro-Glu-Glu-Cys-Gly
Amino acids
DNA
mRNA
Protein

9. Neutral Substitution Normal gene Substitution mutation GGTCTCCTCACGCCA↓
CCAGAGGAGUGCGGU
Codons
Pro-Glu-Glu-Cys-Gly
Amino acids
Substitution mutation
GGTCTTCTCACGCCA ↓
CCAGAAGAGUGCGGU
Pro-Glu-Glu-Cys-Gly

10. Substitution Mutation
Normal gene
GGTCTCCTCACGCCA ↓
CCAGAGGAGUGCGGU
Codons
Pro-Glu-Glu-Cys-Gly
Amino acids
Substitution mutation
GGTCACCTCACGCCA ↓
CCAGUGGAGUGCGGU
Pro-Arg-Glu-Cys-Gly
Substitutions will only affect a single codon.
Their effects may not be serious unless they affect an amino acid that is essential for the structure and function of the finished protein molecule (e.g. Sickle Cell Anemia).

11. Substitution Mutation
Normal gene
GGTCTCCTCACGCCA ↓
CCAGAGGAGUGCGGU
Codons
Pro-Glu-Glu-Cys-Gly
Amino acids
Substitution mutation
GGTCTCCTCACTCCA ↓
CCAGAAGAGUGAGGU
Pro-Glu-Glu-STOP
This substitution mutation changed a normal amino acid codon into a stop codon. Nearly all mutations of this kind lead to non-functional proteins.

12. Frameshift Mutation
The insertion or deletion of a nucleotide results in a frameshift mutation.
This changes the “reading frame” like changing a sentence.
Example:

13. Deletion Mutation
The loss of a nucleotide causes the incorrect grouping of the remaining codons, making all amino acids downstream change.
Normal gene
GGTCTCCTCACGCCA ↓
CCAGAGGAGUGCGGU
Codons
Pro-Glu-Glu-Cys-Gly
Amino acids
Deletion mutation
GGTC/CCTCACGCCA ↓
CCAGGGAGUGCGGU
Pro-Gly-Ser-Ala

14. Insertion Mutation
The addition of a nucleotide in a gene also results in a frameshift mutation.
Normal gene
GGTCTCCTCACGCCA ↓
CCAGAGGAGUGCGGU
Codons
Pro-Glu-Glu-Cys-Gly
Amino acids
Addition mutation
GGTGCTCCTCACGCCA ↓
CCACGAGGAGUGCGGU
Pro-Arg-Gly-Val-Arg

15. What causes Mutations? Errors in DNA replication Chemicals Radiation
Viruses

16. DNA Replication and Cancer
Recall that most errors in DNA replication are repaired.
Unrepaired mutations that affect genes that control cell division can cause diseases such as cancer.

17. Body Cell vs. Sex Cell Mutation
Body cell mutations are not passed on to the next generation.
Mutations that occur in sex cells are passed on to the organism’s offspring and will be present in every cell of the offspring.